package Elementary_algorithm.LinkList;


/*
给你一个链表，删除链表的倒数第n个结点，并且返回链表的头结点。

示例 1：
输入：head = [1,2,3,4,5], n = 2
输出：[1,2,3,5]
示例 2：
输入：head = [1], n = 1
输出：[]
示例 3：
输入：head = [1,2], n = 1
输出：[1]

作者：LeetCode
链接：https://leetcode.cn/leetbook/read/top-interview-questions-easy/xn2925/
 */
public class _02删除链表的倒数第N个节点 {

    public class ListNode {
        int val;
        ListNode next;

        ListNode() {
        }

        ListNode(int val) {
            this.val = val;
        }

        ListNode(int val, ListNode next) {
            this.val = val;
            this.next = next;
        }
    }

    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode dummy = new ListNode(0,head);
        ListNode slow = dummy;
        ListNode fast = head;
        for (int i = 0; i < n; i++) {
            if (fast != null)
                fast = fast.next;
        }
        while (fast != null) {
            fast = fast.next;
            slow = slow.next;
        }
        slow.next = slow.next.next;
        return dummy.next;
    }
}
